Gas-filled amplifying tube



Sept. 3, 1957 V J. G. w. MULDER: I, 2,

GAS-FILLED AMPLIFYING TUBE Filed Jan. 5. 1955 INVENTOR JOHAN NES GUSBERTUS WILHELM AG NT UnitedStates Patent GAS-FILLED MEPLEFYING TUBE Johannes Gijsbertus Wilhelm Mulder, Emmasingel, Eindhoven, Netherlands, assignor, by mesne assignments,

to North American Philips Company, Inc., New York, N. Y., a corporation of Delaware Application January 5, 1955, Serial No. 479,978

Claims priority, appiicah'on Netherlands January 6, 1954 Ciaims. (Cl. 315-115) This invention relates to gas-filled current amplifying discharge tubes.

Tubes of the foregoing type generally contain a vapor filling and, if desired, a gas filling at low pressure, and at least a main anode, a main cathode and an auxiliary cathode. The electrodes are arranged relatively to one another such that ions diffuse from an auxiliary discharge in the path between the auxiliary cathode and the main electrodes into the main discharge path where they neutralize wholly or in part an electron space charge thereat. The auxiliary discharge current is controlled in intensity by for example a series-connected high-vacuum tube or in a direct manner. The magnitude of the auxiliary discharge current determines the extent to which ions diffuse from the auxiliary discharge path into the main discharge path. The density of the ions difiused into the main discharge path in turn determines the intensity of the electron flow which may be produced between the main cathode and the main anode at a predetermined voltage. In this manner, material current amplifications may be obtained. Such a device is described in Electronics, May 1951, page 107 f1, and P. I. R. E. June 1952, page 645 it.

In a known device of this kind, the tube contains a filling of rare gas. This filling of rare gas requires that the gas pressure thereof should have a definite value in order to ensure not too excessive a voltage drop and, hence, consumption of energy in the auxiliary discharge path. However, this value of gas pressure requires that the electrode voltages in the main discharge path below, since arc discharge may otherwise occur independently. Thus, even with high currents in the main discharge path, the obtainable output energy is comparatively small.

The chief object of the invention is to provide a device of the aforesaid kind in which these disadvantages are eliminated.

According to the invention, an electric discharge tube having a vapor filling and, if desired, a gas filling, at low pressure comprises at least an anode, a main cathode and an auxiliary cathode. These electrodes are arranged relatively to one another in a manner such that ions diffuse from the auxiliary discharge path between the auxiliary cathode and the main electrodes into the main discharge path. Means are provided for maintaining a higher pressure in the space around the auxiliary cathode than in the space between the main electrodes. The high pressure around the auxiliary cathode ensures that an auxiliary discharge of sufiicient intensity may be obtained at a comparatively small Voltage difference, whereas due to the lower pressure in the region of the main electrodes, a higher voltage difference may be obtained between these electrodes than with the known devices. In the known devices the ionization voltage of the gas filling is the absolute maximum limit for the voltage difierence in the main discharge.

In the device according to the invention, the desired pressure difference is maintained by a system of evaporation and condensation. Thus, a pressure difference of 1:20 may be readily obtained. The pressure of the gas 2,895,355 Patented Sept. 3, 1957 filling, if any, must be lower than the maximum vapor pressure. A particular advantage of the device according to the invention is that the ion transport against the field in the auxiliary discharge path is improved due to the pressure difference.

The invention will now be described with reference to the accompanying drawing, in which the sole figures show diagrammatically, a device according to the invention.

Referring to the drawing, a gas discharge vessel 1 encloses an auxiliary filament cathode 2, a main filament cathode 3, and a main anode 4. At the bottom end, the discharge vessel includes a storage vessel 5, which is filled with mercury and is surrounded by a heating device 6. The reentrant or narrow communication 7 between the conical bottom part 8 and the spherical top part 9 of the discharge vessel 1 is cooled intensively by a flow of air as indicated by arrows. Due to the heating and cooling, the pressure around the auxiliary cathode 2 is a few times higher than that of the main discharge path between the electrodes 3 and 4. The tube 1 is included in a circuit arrangement comprising a load 10, an anode voltage supply 11, a voltage supply 12 for the auxiliary discharge path and a control-tube 13.

Control-voltage variations in the auxiliary tube 13 produce a current variation in the auxiliary discharge path from 2 to 3 and 4. The auxiliary current variations produce ion density variations in the main discharge path 3 and 4, which act upon the electron fiow between the electrodes 3 and 4. A variation in output current, which is amplified relative to the variations in auxiliary current, is obtained by means of the load 19.

Typical dimensions for one embodiment of a device according to the invention are as follows: the electrodes 3 and 4 were spaced apart about 2 cm. The electrode 2 u was spaced about 10 cm. from the main discharge path between the electrodes 3 and 4. The mercury vapor pressure in the region surrounding the auxiliary cathode 2 was about 0.2 mm. The mercury vapor pressure in the region surrounding the main electrodes 3, 4 was about 0.015 mm. The potential source 11 had a value of about 300 v. and the source 12 a value of about v. The current amplification was about tenfold. A gas filling may be added to the mercury vapor. A suitable gas is helium at a pressure lower than that of the maximum vapor pressure of the mercury, e. g. 0.05 mm.

While I have described our invention in connection with specific embodiments and applications, other modifications thereof will be readily apparent to those skilled in this art without departing from the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. An electric discharge device containing an ionizable filling, said device comprising at least a main anode and a main cathode defining a main discharge path, a load circuit coupled to said main anode and cathode, an auxiliary cathode defining an auxiliary discharge path with said main electrodes, a control circuit coupled to said auxiliary cathode, and means for maintaining the space around the auxiliary cathode at a higher pressure than the space between the main electrodes.

2. A device as claimed in claim 1 wherein the lastnamed means involves a system of evaporation and condensation.

3. An electric discharge device comprising an envelope with a reentrant portion dividing the envelope into two communicating regions, main anode and cathode electrodes in one of said regions defining a discharge path therebetween, a load circuit coupled to said main electrodes, an auxiliary cathode in the other of said regions defining an auxiliary discharge path with said main electrodes, a source of ionizable vapor-producing material communicating with said other region, means for evaporating said material to produce vapor in said other region at a given pressure, means for condensing said vapors disposed between said regions to reduce the vapor pressure in said one region whereby the pressure in said one region is substantially below said given pressure, and means coupled to said auxiliary cathode for controlling the magnitude of the auxiliary discharge and thereby controlling the diflusion of ions into the main discharge path and the magnitude of the main discharge.

4. An electric discharge device as claimed in claim 3 wherein the evaporating means includes heating means,

and the condensing means includes means for passing cool air about the reentrant portion of the envelope.

5. A device as claimed in claim 3 wherein a gas filling is provided in the envelope at a lower pressure than the maximum vapor pressure. 7

1,808,517 1,863,702 Smith June 21, 1932 2,445,075 Mulder et al July 13, 1948 

